Automated assembly method and automated assembly apparatus

ABSTRACT

An automated assembly apparatus, characterized by comprising an assembly robot having a plurality of hands, the plurality of hands being movable in an X-axis direction and a Y-axis direction by an X-axis moving unit and a Y-axis moving unit, and a plurality of workbenches which are provided with Z-axis moving unit and which are movable in a Z-axis direction by the Z-axis moving unit. A work area is independently provided for the plurality of workbenches, a width of a predetermined work area among the work areas is larger than clearance widths of the plurality of hands, widths of the work areas other than the predetermined work area are smaller than the clearance widths of at least some of the plurality of hands, and the hand which performs a job on the predetermined work area is disposed at a lowermost level in the Z-axis direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automated assembly method that uses an automated assembly apparatus having an assembly robot with a plurality of hands, and an automated assembly apparatus.

2. Description of the Related Art

Conventionally, when performing a plurality of jobs by a single robot in an automated assembly apparatus, a tool changer has been used to change a hand. However, there has been a problem in that the use of the tool changer to change a hand or tool inconveniently takes time, resulting in an increased cycle time. Hence, there is a demand for a robot hand capable of performing a plurality of jobs while minimizing the changing time.

As a means for solving the aforesaid problem, Japanese Patent Application Laid-Open No. H08-323559 describes a robot hand apparatus having a single robot provided with three hands, namely, a swaging hand, a shaft chuck hand, and a gear chuck hand. The use of the means described in Japanese Patent Application Laid-Open No. H08-323559 enables a single robot to promptly perform a plurality of jobs.

However, the robot hand apparatus described in Japanese Patent Application Laid-Open No. H08-323559 is adapted to perform jobs by an articulated robot, which has one hand in a direction perpendicular to a tool adapter and two hands in a direction parallel thereto. This means that the robot hand apparatus does not enable an orthogonal robot to perform jobs. In addition, the hands have to be sufficiently spaced away from each other so as to prevent hands from interfering with a hand performing a job, thus resulting in an increased space required for performing jobs.

An object of the present invention is to solve problems that cannot be solved by conventional techniques and therefore to provide an automated assembly method and an automated assembly apparatus that enable an orthogonal robot to perform jobs, ensure no interference among hands, and permit higher space efficiency.

SUMMARY OF THE INVENTION

To this end, an automated assembly apparatus in accordance with the present invention includes:

an assembly robot having a plurality of hands, the plurality of hands being movable in an X-axis direction and a Y-axis direction by an X-axis unit and a Y-axis unit; and

a plurality of workbenches which are provided with Z-axis units and which are movable in a Z-axis direction by the Z-axis units,

wherein a work area is independently provided for the plurality of the workbenches,

a width of a predetermined work area among the work areas is larger than clearance widths of the plurality of hands,

the widths of the work areas other than the predetermined work area are smaller than the clearance widths of at least some of the plurality of hands, and

the hand which performs a job on the predetermined work area is placed at a lowermost level in the Z-axis direction.

To this end, an automated assembly method in accordance with the present invention uses an automated assembly apparatus that includes an assembly robot having a plurality of hands which are movable in an X-axis direction and a Y-axis direction by an X-axis unit and a Y-axis unit, and a plurality of workbenches which are provided with Z-axis units and which are movable in a Z-axis direction by the Z-axis units,

wherein the plurality of the workbenches has an independent work area,

a width of a predetermined work area among the work areas is set to be larger than a width that permits entry of the plurality of hands,

wherein the widths of the work areas other than the predetermined work area are set to be smaller than a width that permits entry of at least some of the plurality of hands, and

a hand which performs a job on the predetermined work area is disposed at a lowermost level in the Z-axis direction among the plurality of hands, and

wherein the assembly robot is moved in the X-axis direction and the Y-axis direction at above the work areas and the workbenches are moved in the Z-axis direction to perform assembly.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an automated assembly apparatus for explaining an automated assembly method illustrating an embodiment of the present invention.

FIG. 2A and FIG. 2B are side views of a plurality of hands in the embodiment of the present invention performing jobs, wherein FIG. 2A illustrates a transferring hand which is performing a job on a first workbench unit, and FIG. 2B illustrates an assembling hand performing a job on a supply unit.

FIG. 3A and FIG. 3B are schematic perspective views of workbench units in the embodiment of the present invention, wherein FIG. 3A is a schematic perspective view of a workbench unit capable of assembly from the directions of three planes, and FIG. 3B is a schematic perspective view of a workbench unit capable of assembly from the directions of five planes.

FIG. 4 is a schematic side view of the automated assembly apparatus, illustrating the relationship between the width of each hand and each work area in a horizontal direction.

FIG. 5 is a schematic side view of the automated assembly apparatus, illustrating the relationship between each hand and a supply tray in a vertical direction.

FIG. 6 is a schematic top view of the automated assembly apparatus, illustrating the relationship of entry in the horizontal direction between each work area and each hand.

DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.

An object of the present invention is to solve the problems that cannot be solved by conventional techniques, and the invention relates to an automated assembly method and an automated assembly apparatus which enable an orthogonal robot to perform jobs, ensure no interference among hands, and permit higher space efficiency.

Embodiments of the automated assembly method and the automated assembly apparatus will be described with reference to the accompanying drawings. In the drawings, like components will be assigned like reference numerals.

EMBODIMENT

Referring to FIG. 1, a basic embodiment to which the present invention is applied will be specifically described below. FIG. 1 is a schematic perspective view of an automated assembly apparatus according to the present invention.

An automated assembly apparatus 1 includes an assembly robot 3, an assembly workbench unit 4, a loading workbench unit 5, a positioning unit 6, a supply unit 7, and a screw supply unit 8, each of which is disposed on a base 2 and movable in a horizontal plane.

The supply unit 7 has a supply tray 10 which accommodates at least one or more assembly components 9 such that the assembly components 9 can be supplied. The assembly components 9 on the supply tray 10 are picked up from the supply tray 10 and grasped by an assembling hand 15, which will be discussed hereinafter.

Each of the assembly workbench unit 4, the loading workbench unit 5, the positioning unit 6, the supply unit 7, and the screw supply unit 8 has an independent work area.

The assembling hand 15, a transferring hand 16, and a screw tightening unit 17 are disposed such that, when performing jobs in the work areas of the assembly workbench unit 4, the loading workbench unit 5, the positioning unit 6, and the screw supply unit 8, no other hands enter these work areas. However, the work area of the supply unit 7 has a width in the horizontal direction that allows other hands to enter while the assembling hand 15 is performing a job.

The assembly robot 3 includes a Y-axis mover (Y-axis moving unit) 12, which is provided on support columns 11 fixed on the base 2, and an X-axis mover (X-axis moving unit) 13 movably installed on the guide rail of the Y-axis mover 12. The assembly robot 3 does not have a drive unit in a Z-axis direction. The guide rail of the X-axis mover 13 is provided with a plurality of hands 14. The plurality of hands 14 include the assembling hand 15, the transferring hand 16, and the screw tightening unit 17, which are disposed in parallel in the Y-axis direction.

The assembling hand 15 has a through hole 18 b as a guiding means that permits positioning relative to a workbench 21 a, which will be discussed hereinafter. The X-axis and the Y-axis are substantially orthogonal to each other and lie in the same plane.

The assembly workbench unit 4 is a unit adapted to position and holds an assembly target component 19 in order to assemble the assembly component 9 to the assembly target component 19. The assembly workbench unit 4 is comprised of a carrier 28, a Z-axis mover (Z-axis moving unit) 20 a, the workbench 21 a, a work holder 22 for positioning and holding the assembly target component 19, a guide 18 a, and a compliance mechanism (profiler) 23, which is movable in the X-axis direction, the Y-axis direction and a rotational direction.

The compliance mechanism (profiler) 23 has a locking and unlocking mechanism, which unlocks to enable the workbench 21 a to move when positioning the workbench 21 a relative to the assembling hand 15. The compliance mechanism 23 may be provided with a first rotator 24, which remains locked except for the positioning, thereby allowing the workbench 21 a to rotate.

The loading workbench unit 5 is adapted to load the assembly target component 19 onto the automated assembly apparatus 1. The loading workbench unit 5 is capable of positioning and holding the assembly target component 19, as with the assembly workbench unit 4, and is comprised of a Z-axis mover 20 b and a workbench 21 b. The assembly workbench unit 4, which is a holding means, may be provided with an operating means that can be operated in the directions of a plurality of axes (two or more axes).

An operator places the assembly target component 19 on the workbench 21 b, and positions and holds the assembly target component 19 by operating a control panel (not illustrated). Alternatively, the assembly target component 19 may be carried by a carrier (not illustrated) to the loading workbench unit 5.

The positioning unit 6 is adapted to perform highly accurate assembly by positioning the assembly component 9 in advance, and has a positioning table 26 placed on a Z-axis mover 20 c. Disposed on the positioning table 26 is a positioner 27, which engages the assembly component 9 to set the phase of the rotational direction and the position in the XY-axis direction of the assembly component 9 with high accuracy.

The supply unit 7 is adapted to store and supply the assembly component 9, and has the supply tray 10 placed on a Z-axis mover 20 d. A plurality of assembly components are placed in parallel on the supply tray 10, thus allowing the plurality of parts to be supplied. A plurality of types of assembly components may be placed in the supply tray 10. Further alternatively, a plurality of types of supply trays may be arranged to supply a plurality of types of parts. Further, the screw supply unit 8 is adapted to store and supply screws, and provided with a Z-axis mover 20 e at the distal end thereof.

FIG. 2A and FIG. 2B illustrate the layout of the assembling hand 15, the transferring hand 16 and the screw tightening unit 17, which constitute the plurality of hands 14. FIG. 2A illustrates the transferring hand 16 in the process of transferring the assembly target component 19 from the workbench 21 a of the assembly workbench unit 4.

Further, FIG. 2B illustrates the assembling hand 15 performing a job on the supply unit 7. The assembling hand 15 is mounted at the lowermost level in the Z-axis direction in relation to the transferring hand 16 and the screw tightening unit 17. As illustrated in FIG. 2B, the heights of the assembling hand 15, the transferring hand 16 and the screw tightening unit 17 are different from each other. Further, the heights are set such that the lowermost parts of the transferring hand 16 and the screw tightening unit 17 do not come in contact with the supply tray 10 when the assembling hand 15 performs a job on the assembly components 9 placed on the supply tray 10.

FIG. 3A and FIG. 3B are the schematic perspective views of the assembly workbench unit 4. FIG. 3A illustrates a state in which the assembly from three plane directions can be performed by the first rotator 24. Further, as illustrated in FIG. 3B, a second rotator 25 may be provided to permit the assembly from five plane directions.

A specific description will now be given of a series of operations of the automated assembly apparatus according to the embodiment of the present invention with reference to FIG. 1.

First, the assembly target component 19 is placed on the workbench 21 b by an operator or a carrier (not illustrated).

After placing the assembly target component 19, the transferring hand 16 provided on the assembly robot 3 is moved onto the loading workbench unit 5 by operating the Y-axis mover 12 and the X-axis mover 13. After the movement of the transferring hand 16 onto the loading workbench unit 5 is completed, the Z-axis mover 20 b provided on the loading workbench unit 5 ascends, and the transferring hand 16 grasps the assembly target component 19 placed on the workbench 21 b.

When the assembly target component 19 is grasped, the Z-axis mover 20 b descends. After the descent, the Y-axis mover 12 and the X-axis mover 13 are operated to move the transferring hand 16 provided on the assembly robot 3 onto the assembly workbench unit 4. After the movement of the transferring hand 16 onto the assembly workbench unit 4 is completed, the Z-axis mover 20 a provided on the assembly workbench unit 4 moves up and the transferring hand 16 unchucks, i.e. clears grasping, thereby setting the assembly target component 19 on the workbench 21 a. After the Z-axis mover 20 a descends, the work holder 22 advances to position and retain the assembly target component 19.

Next, the Y-axis mover 12 and the X-axis mover 13 are operated to move the assembling hand 15 provided on the assembly robot 3 onto the supply unit 7. After the movement of the assembling hand 15 onto the supply unit 7 is completed, the Z-axis mover 20 d provided on the supply unit 7 ascends, and after the ascent, the assembly component 9 placed in the supply tray 10 is grasped by the assembling hand 15.

After the supply unit 7 is moved down by operating the Z-axis mover 20 d, the Y-axis mover 12 and the X-axis mover 13 are operated to move the assembling hand 15 onto the positioning unit 6. Following the completion of the movement of the assembling hand 15 onto the positioning unit 6, the Z-axis mover 20 c provided on the positioning unit 6 ascends. After the ascent, the assembling hand 15 unchucks the assembly component 9, and places the assembly component 9 on the positioning table 26.

After the assembling hand 15 unchucks the assembly component 9, the positioner 27 advances to enhance the accuracy of the position in the XY direction and the phase direction of the assembly component 9. The assembly component 9 which has been positioned with higher accuracy is re-grasped by the assembling hand 15. The operation that involves the positioning unit 6 may be performed only when a high-accuracy assembling operation is required, and therefore may not be necessarily performed.

Upon the completion of the operation by the positioning unit 6, the Y-axis mover 12 and the X-axis mover 13 are operated to move the assembling hand 15 onto the assembly workbench unit 4. After the movement of the assembling hand 15 onto the assembly workbench unit 4 is completed, the compliance mechanism (profiler) 23 unlocks to enable the workbench 21 a to move.

After the workbench 21 a becomes movable, the workbench 21 a is moved up by the Z-axis mover 20 a provided on the assembly workbench unit 4. As the workbench 21 a moves up, the pin-shaped guide 18 a fits in the through hole 18 b, thereby moving the workbench 21 a by the compliance mechanism (profiler) 23 so as to be positioned with respect to the assembling hand 15.

With the workbench 21 a positioned, the workbench 21 a is further moved up to fit the assembly component 9 grasped by the assembling hand 15 onto the assembly target component 19 positioned and retained on the workbench 21 a. After the fitting, the assembling hand 15 unchucks the assembly component 9, and the workbench 21 a is moved down by the Z-axis mover 20 a.

After the fitting of the assembly target component 19 and the assembly component 9, the Y-axis mover 12 and the X-axis mover 13 are operated to move the screw tightening unit 17 onto the screw supply unit 8. At the same time, a driver bit (not illustrated) in the screw tightening unit 17 is rotated by a motor (not illustrated) provided in the screw tightening unit 17.

After the completion of the movement of the screw tightening unit 17 onto the screw supply unit 8, the screw tightening unit 17 performs suction by a suctioner (not illustrated). As the Z-axis mover 20 e ascends, the screw supply unit 8 ascends with a screw held at the distal end thereof and stops in the vicinity of the screw tightening unit 17 performing the suction. Then, the screw is handed to the screw tightening unit 17.

After the Z-axis mover 20 e descends to move the screw supply unit distal end down, the Y-axis mover 12 and the X-axis mover 13 are operated to move the screw tightening unit 17 onto the assembly workbench unit 4. After the movement of the screw tightening unit 17 onto the assembly workbench unit 4 is completed, the workbench 21 a is moved up by the Z-axis mover 20 a provided on the assembly workbench unit 4. In the middle of the ascent, when the screw and the assembly target component 19 come in contact with each other, a torque change starts, and the torque reaches a maximum value upon the completion of tightening the screw. The instant the maximum value of the torque is detected, the motor (not illustrated) of the screw tightening unit 17 and the Z-axis mover 20 a stop.

After assembling the assembly component 9 to the assembly target component 19 as described above, the assembly component 9 may be fixed to the assembly target component 19 by the screw tightening unit 17. Further, the screw tightening unit 17 and the screw supply unit 8 are necessary only when a screw tightening process is involved, and the screw tightening process is not necessarily carried out. Therefore, the screw tightening unit 17 and the screw supply unit 8 may be attached or detached, as necessary. Further, using the first rotator 24 and the second rotator 25 makes it possible to perform an operation for assembling the assembly component 9 to the assembly target component 19 in a plurality of directions or to perform a fixing operation, such as tightening screws.

When the assembly component 9 is fitted or connected to the assembly target component 19 and the assembly process on the automated assembly apparatus 1 is finished, the carrier 28 provided on the assembly workbench unit 4 is operated to discharge the assembly target component 19 set on the workbench 21 a out of the automated assembly apparatus 1.

Referring now to FIG. 4 and FIG. 5, a description will be given of the relationship between the width of each hand and each work area in the horizontal direction and the relationship between each hand and the supply tray in the vertical direction. FIG. 4 is a schematic side view of the automated assembly apparatus, illustrating the relationship between the width of each hand and each work area in the horizontal direction. Further, FIG. 5 is a schematic side view of the automated assembly apparatus, illustrating the relationship between each hand and the supply tray in the vertical direction.

Referring to FIG. 4, a work area As of the workbench 21 a of the assembly workbench unit 4, a work area Ai of the positioning table 26, and a work area Ak of the supply tray 10 are provided as illustrated in the drawing. Further, the transferring hand 16 and the screw tightening unit 17 constituting the plurality of hands 14 have clearance widths Bi and Bs, respectively, for entering the work areas.

In FIG. 4, the sizes of widths Ws, Wi and Wk of the work areas As, Ai and Ak denote the sizes in the horizontal direction (the Y-axis direction in this case). The clearance widths Bi and Bs of the hands also denote the sizes in the horizontal direction.

The relationship between the width of each work area and the clearance width of each hand is denoted as shown below.

Ws<Bs,Ws<Bi  (1)

Wi<Bs,Wi<Bi  (2)

Wk>Bs,Wk>Bi  (3)

As indicated by (1) and (2) above and FIG. 4, the work area As of the workbench 21 a and the work area Ai of the positioning table 26 are set to be slightly smaller than the clearance width Bs and the clearance width Bi. Thus, the transferring hand 16 and the screw tightening unit 17 cannot enter the work areas As and Ai except for the work area Ak of the supply tray 10.

As described above, the widths of the work areas other than a predetermined work area are set to be smaller than the clearance widths of at least some of the plurality of hands, and the width of the predetermined work area among the work areas is set to be larger than the clearance widths of the plurality of hands, as indicated by (3) above.

Thus, according to the present invention, if, for convenience, the width of a predetermined work area is denoted by Wx (Wk), the widths of the work areas other than the predetermined work area are denoted by Wy, and the width that allows the plurality of hands to enter is denoted by Bx, then a relationship expressed by Wx>Bx and Wy<Bx is satisfied.

As described above, the widths of the work areas other than a predetermined work area (the work area of the supply tray in the present embodiment) are set to widths that block the entry of at least some of the plurality of hands. Hence, the width of each workbench (work area) is adjusted to the width of each hand, so that each hand can be disposed with smaller intervals. This provides an advantage of improved space efficiency.

If the predetermined work area is the supply tray 10, on which the plurality of assembly components 9 are placed in parallel to be supplied to the assembling hand 15, then the assembly components 9 on the supply tray 10 are grasped and transferred by the assembling hand 15 as the predetermined hand. At this time, the assembling hand 15 is disposed at the lowermost level in the Z-axis direction.

Referring now to FIG. 5, the relationship between each hand and the supply tray in the vertical direction, i.e. the Z-axis direction, will be described. The uppermost part of the supply tray 10 is movable from the base 2 up to a height Ht by the Z-axis mover 20 d. Meanwhile, the heights of the lowermost parts of the assembling hand 15, the transferring hand 16 and the screw tightening unit 17, which do not descend themselves, from the base 2 are denoted by Hk, Hi and Hs.

The height relationship between each hand and the supply tray 10 (the relationship in the vertical direction) is expressed as follows.

Ht<Hk,Ht=Hk  (1)

Ht<Hi,Ht<Hs  (2)

Before the assembling hand 15 moves onto the supply tray 10, the supply tray 10 is positioned at a level that is lower than the height Hk so as not to interfere with the movement of the assembling hand 15. When the assembling hand 15 reaches the position where the assembly component 9 on the supply tray 10 can be grasped, the assembling hand 15 is controlled by a controller (not illustrated) to move up to the height Ht.

Thus, if, for convenience, the height of a hand that performs a job on a predetermined work area is denoted by Hx, the heights of other hands are denoted by Hy, and the height at which the uppermost part of the predetermined work area has ascended most is denoted by Hz, then the relationship expressed by Hx<Hz and Hy>Hz is satisfied.

As seen from FIG. 5, among the plurality of hands having different heights, the assembling hand 15, which performs a job on a first work area, is disposed at the lowermost level in the Z-axis direction. This makes it possible to avoid interference without increasing the intervals among the plurality of hands, so that the hands can be disposed with smaller intervals in the width direction, thus enabling an orthogonal robot to perform jobs. Further, each workbench independently moves up and down, so that the workbenches can be disposed with smaller intervals thereamong, resulting in higher space efficiency of the entire apparatus.

FIG. 6 is a schematic plan view of the automated assembly apparatus, illustrating the relationship between each work area and the entry of each hand in the horizontal direction. The drawing illustrates the assembling hand 15 performing a job on the supply tray 10. At this time, the assembly robot 3 provided with the plurality of hands enters the work area in the XY-axis direction of the supply tray 10.

The work area Ak of the supply tray 10, which is the first work area, has the width Wk in the horizontal direction that allows the other hands, namely, the transferring hand 16 and the screw tightening unit 17, to enter while the assembling hand 15 is working in the work area Ak. Hence, as illustrated in FIG. 6, the plurality of hands, namely, the assembling hand 15, the transferring hand 16 and the screw tightening unit 17, can enter the work area Ak.

Meanwhile, an arrangement is made such that, while one of the assembling hand 15, the transferring hand 16, and the screw tightening unit 17 performs a job in a work area other than the work area Ak of the supply tray 10, other hands do not enter the particular other work area.

According to the configuration and the operations described above, the width of the work area other than the supply unit 7 is the width that prohibits an adjacent hand from entering the work area. Further, the assembling hand 15 is placed at the lowermost level in the Z-axis direction with respect to the other hands so as to allow the hands to be disposed with smaller intervals in the width direction. Further, each of the workbenches independently moves up and down, so that the work areas can be disposed with smaller intervals thereamong, resulting in higher space efficiency of the entire automated assembly apparatus.

Further, the plurality of assembly components 9 are placed in parallel on the supply tray 10, and the supply tray 10 moves up and down in the Z-axis direction, so that a plurality of parts can be supplied with the parts retained in the supply tray. This obviates the need for an additional transferring mechanism, thus permitting a simplified supply system.

The automated assembly apparatus in accordance with the present invention provides the following advantages.

In the automated assembly apparatus in accordance with the present invention, among the work areas of the plurality of workbenches, the width of a predetermined work area is set to be larger than the clearance widths of the plurality of hands, and the widths of the work areas other than the predetermined work area are set to be smaller than the clearance widths of at least some of the plurality of hands. Further, the hand performing a job on a predetermined work area is disposed at the lowermost level in the Z-axis direction. Hence, the interference among the plurality of hands can be avoided without increasing the intervals thereamong, so that the hands can be disposed with smaller intervals in the width direction, and jobs can be performed by an orthogonal robot. Further, since each workbench independently moves up and down, the workbenches can be disposed with smaller intervals, resulting in higher space efficiency of the entire apparatus.

Further, in the automated assembly apparatus according to the present invention, a plurality of parts are placed in parallel on the tray and the supply parts on the tray are grasped and transferred by a first hand. Hence, a plurality of parts can be supplied with the parts held in the tray, thus permitting a simplified supply system by eliminating the need for a transferring mechanism even when an orthogonal robot is used.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2015-070769, filed Mar. 31, 2015, and Japanese Patent Application No. 2016-049385, filed Mar. 14, 2016, which are hereby incorporated by reference herein in their entirety. 

What is claimed is:
 1. An automated assembly apparatus, characterized by comprising: an assembly robot having a plurality of hands, the plurality of hands being movable in an X-axis direction and a Y-axis direction by an X-axis moving unit and a Y-axis moving unit; and a plurality of workbenches which are provided with Z-axis moving unit and which are movable in a Z-axis direction by the Z-axis moving unit, wherein a work area is independently provided for the plurality of workbenches, a width of a predetermined work area among the work areas is larger than clearance widths of the plurality of hands, widths of the work areas other than the predetermined work area are smaller than the clearance widths of at least some of the plurality of hands, and the hand which performs a job on the predetermined work area is disposed at a lowermost level in the Z-axis direction.
 2. The automated assembly apparatus according to claim 1, wherein the assembly robot does not have a drive unit in the Z-axis direction.
 3. The automated assembly apparatus according to claim 1, wherein the predetermined work area is a supply tray on which a plurality of assembly components are placed.
 4. The automated assembly apparatus according to claim 1, wherein, in the case where the width of the predetermined work area is denoted by Wx, the widths of the work areas other than the predetermined work area are denoted by Wy, and the width that permits the entry of the plurality of hands is denoted by Bx, a relationship expressed by Wx>Bx and Wy<Bx is satisfied.
 5. The automated assembly apparatus according to claim 1, wherein, in the case where a height of a hand which performs a job on the predetermined work area is denoted by Hx, heights of other hands are denoted by Hy, and a height of an uppermost part of the predetermined work area at the time of reaching a highest level is denoted by Hz, a relationship expressed by Hx<Hz and Hy>Hz is satisfied.
 6. The automated assembly apparatus according to claim 1, wherein, in the case where the width of the predetermined work area is denoted by Wx, the widths of the work areas other than the predetermined work area are denoted by Wy, and a width that permits the entry of the plurality of hands is denoted by Bx, a relationship expressed by Wx>Bx and Wy<Bx is satisfied, and wherein, in the case where the height of a hand which performs a job on the predetermined work area is denoted by Hx, the heights of other hands are denoted by Hy, and the height of the uppermost part of the predetermined work area at the time of reaching a highest level is denoted by Hz, a relationship expressed by Hx<Hz and Hy>Hz is satisfied.
 7. An automated assembly method, characterized by using an automated assembly apparatus which includes an assembly robot having a plurality of hands, the plurality of hands being movable in an X-axis direction and a Y-axis direction by an X-axis moving unit and a Y-axis moving unit; and a plurality of workbenches which are provided with a Z-axis moving unit and which are movable in a Z-axis direction by the Z-axis moving unit, wherein the plurality of workbenches has an independent work area, a width of a predetermined work area among the work areas is set to be larger than a width which permits entry of the plurality of hands, wherein the widths of the work areas other than the predetermined work area are set to be smaller than a width which permits entry of at least some of the plurality of hands, and a hand that performs a job on the predetermined work area is disposed at a lowermost level in the Z-axis direction among the plurality of hands, and wherein the assembly robot is moved in the X-axis direction and the Y-axis direction at above the work areas to move the workbenches in the Z-axis direction, thereby performing assembly.
 8. The automated assembly method according to claim 7, wherein the assembly robot does not have a drive unit in the Z-axis direction.
 9. The automated assembly method according to claim 7, wherein the predetermined work area is a supply tray on which a plurality of assembly components are placed.
 10. The automated assembly method according to claim 7, wherein, in the case where a width of the predetermined work area is denoted by Wx, widths of the work areas other than the predetermined work area are denoted by Wy, and a width that permits the entry of the plurality of hands is denoted by Bx, a relationship expressed by Wx>Bx and Wy<Bx is satisfied.
 11. The automated assembly method according to claim 7, wherein, in the case where a height of a hand that performs a job on the predetermined work area is denoted by Hx, heights of other hands are denoted by Hy, and a height of an uppermost part of the predetermined work area at the time of reaching a highest level is denoted by Hz, a relationship expressed by Hx<Hz and Hy>Hz is satisfied.
 12. The automated assembly method according to claim 7, wherein, in the case where the width of the predetermined work area is denoted by Wx, the widths of the work areas other than the predetermined work area are denoted by Wy, and the width that permits the entry of the plurality of hands is denoted by Bx, a relationship expressed by Wx>Bx and Wy<Bx is satisfied, and wherein, in the case where the height of a hand that performs a job on the predetermined work area is denoted by Hx, the heights of other hands are denoted by Hy, and the height of the uppermost part of the predetermined work area at the time of reaching a highest level is denoted by Hz, a relationship expressed by Hx<Hz and Hy>Hz is satisfied. 